Answer:
For the Second Athenian Confederacy (378-7 BC), a revival of the Delian League, the enemy was Sparta. It was created as a protection against Spartan aggression. It was a maritime self-defense league led by Athens. The Delian League was finally broken up by the capture of Athens by Sparta in 404 BC.
In my opinion, it was because the agricultural revolution mainly.
It is important because in 1836, during the Texas Revolution, somewhere around 200 rebels including Davy Crockett and James Bowie held out against 1,800 Mexican Soldiers under the command of Santa Anna, the Mexican dictator at the time, for thirteen days.
1) The Keating-Owen Act of 1916 passed under Wilson's New Freedom.
2) Group A is the result of the Progressive Era. Direct election of senators is a dead giveaway.
3) The Populist Party, according to some historians, had a close link with the Progressives. This is debatable though.